Dengue is the most prevalent mosquito-borne viral disease causing disease in humans. Dengue disease may present as a non-specific febrile illness, dengue fever (DF), or as a more severe infection marked by hemorrhage or circulatory failure or shock, dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS). There are currently no licensed vaccines or therapeutics for dengue virus (DENV). Our laboratory has optimized and utilized human ex vivo models for virus infections, which have been very useful for elucidating mechanisms of innate immune evasion by DENV in specific cell types. Understanding virus-host interactions during DENV infections and the molecular mechanisms involved in the generation of immune responses is one of the crucial factors that will lead to the development of effective and safe vaccines and therapeutics. This project will analyze immune responses to DENV infections ex vivo using two robust systems of human PBMCs and DCs, which are targets for DENV infection in humans. This controlled system of DENV infection captures early events of the virus-host interaction. We will profile innate immune responses to DENV primary isolates circulating in Nicaragua (Project 1) and DENV vaccine strains (Takeda Vaccines Inc., Project 2). Selected strains will be then used for the in depth characterization of the innate immune response, cellular transcriptome, epigenome and proteome in collaboration with the Genomics (Core B), Proteomics (Core C) and immune monitoring Core (Core D) in PBMCs or DCs upon viral exposure. We will identify host proteins that differentially mediate innate immune responses and impact viral replication with the same DENV isolates and vaccines strains by siRNA screens in DCs. Data will be managed and analyzed by the Data Analysis and Modeling Core (Core E) and the Data Management and Dissemination Core (Core F) to define parameters and build cellular and molecular networks important for innate immunity to DENV. Networks will be subsequently integrated with those generated from in vivo studies in Projects 1 (natural infections) and 2 (vaccine trials). Also, our ex vivo systems will serve to identify sets of genes through global analysis to design targeted assays for in vivo studies in Projects 1 and 2 and to validate the role of specific genes important for innate immunity to DENV infection identified in vivo.